THORNTON – It was supposed to be a “bloodless bullfight,” a dangerous dance between a pirouetting matador and an enraged bull that would not end in death.

But this time-honored Portuguese tradition capping a religious festival was anything but bloodless.

As the matador raised a short festooned spear to stick to the bull’s neck, an animal welfare investigator charged into the ring, suspecting that the banderilla’s Velcro tip concealed an illegal steel barb that would pierce the animal’s hide.

Spectators chased down the intruder, and a bloody melee ensued, sending a San Joaquin County Sheriff’s deputy to the hospital and two men to jail.

The episode in May reignited a battle that has endured for several decades between the bullfight aficionados and animal welfare advocates who contend the ritual is animal cruelty masquerading as religious theater.

“The Portuguese people wonder why these animal rights activists can come in and disrupt a legal event without any consequences whatsoever,” Frank Sousa, director of the Center for Portuguese Studies University of Massachusetts Dartmouth. “They feel their culture is disrespected. How is it any different from a rodeo?”

When California lawmakers banned to-the-death bullfights in 1957, they created an exemption for Portuguese-style bloodless fights if they are part of religious celebrations, the only exemption in the U.S.

Since then, 20 times every summer across California’s Central Valley, gaily attired matadors on horseback run bulls to exhaustion and taunt them with red capes. In the fight finale, teams of men known as “suicide squads” stop the charging bull in its tracks, then grab the tail and ski around the arena.

Animal welfare advocates say there is nothing religious about a bullfight and they are lobbying for laws to at least require veterinarians on the scene.

“When it gets to the point where they create these bullfights, pretend they’re religious, then torture and slaughter the bulls, I have a big problem,” said attorney David Casselman of the nonprofit Animal Cruelty Investigators, whose agents are monitoring the fights.

The Portuguese community, which forms the backbone of the state’s powerful dairy industry, is girding itself for a public relations fight over an Old World custom falling out of favor in a modern society.

“We need to defend our traditions,” said Jose Avila, publisher of the Portuguese Tribune, one of the largest Portuguese-language weekly newspapers in the nation. “I understand that some people do not like bullfighting, the way I do not like boxing, but we accept the difference, right?”

Avila, whose paper covers nearly every fight in the Central Valley, likened the interaction between bull and matador to the artistry of a painting. He said the bulls are treated well and raised “like kings” to prepare for their life’s mission: a single trip into the arena.

After the fight, they become ring savvy, unpredictably dangerous and are butchered for food.

Whether the bullfights are a religious exercise has been debated since 1981, when then-Attorney General George Deukmejian said the fights would have to be an integral part of a Mass, which must take place on consecrated ground, to comply with the law.

“It’s just crazy what’s going on at these places,” said Andrew Stewart, the ACI’s animal welfare investigator who stopped the fight in May.

He had received a complaint that the bloodless bullfights by professional matadors from Spain, Portugal and Mexico were anything but. A week before the Thornton fight, he found 30 barbed banderillas at a bullfight in Los Angeles County, where authorities now are investigating possible misdemeanor violations of animal cruelty laws.

As for the bullfight in Thornton, allegations of animal cruelty could not be substantiated because someone made off with the banderillas before authorities could inspect them, said San Joaquin County Deputy District Attorney Robert Himelblau.

A spectator accused of assaulting the deputy with a garbage can will have his record cleared if he stays out of trouble for a year.

“At this point, we’re just saying it’s a bad scene. We’re done with it,” Himelblau said, nothing that the law gives wide leeway to the religious practices whether that means Appalachian snake handling or the Santeria practice of animal sacrifices.

The Humane Society of the United States has investigated bloodless bullfights since 1976 and believes they violate state law, but officials say they have had trouble finding a district attorney willing to prosecute.

“We were told by one DA in one case that there was no way he could go up against a priest,” said Eric Sakach, the group’s senior law enforcement specialist. “In a cultural and sociological context, it’s a very interesting story.

“It should make people question how we sometimes treat animals and what excuses we use to treat them badly,” he said.

The recent scrutiny of their tradition has caused Portuguese bullfight fans to fear their community is losing its political clout.

“In the old days we used to invite the congressmen, the assemblymen, the mayors, the sheriff, all these people, but for some reason that we cannot understand, we stopped doing that,” Avila said. “So for maybe 20 years we did not connect with the political power, and we can see now that is not good.”